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. 2022 Aug 18;25(9):104981. doi: 10.1016/j.isci.2022.104981

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This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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β-deligation mechanism of MMACHC

Cyanocobalamin and alkylcobalamins undergo reduction to cob(II)alamin, which is channeled to methionine synthase (MS) or via adenosylcobalamin transferase (ATR) to methylmalonyl-CoA mutase (MUT) to yield the respective biologically active forms, MeCbl and AdoCbl, respectively. Decyanation requires flavin coenzymes FMN or FAD and NADPH. Dealkylation proceeds in the presence of glutathione (GSH) to generate a cob(I)alamin thatundergoes oxidation to the cob(II)alamin cofactor form. The MMACHC bound cob(II)alamin binds to cysteine-261 of the adaptor protein MMADHC forming a protein-linked thiolatocobalamin (Li et al., 2020b).